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Science lesson plan · 7th grade (Year 8 in England) · 30 minutes

Microscopes and magnification

Cells, genetics and evolution

CCSS NGSS.MS-LS1-1England: KS3 Biology: Cells and organisationEngland: KS4 Combined Science: Cell biology

Objective and success criteria

Students will: Microscopes and magnification.

  • I can answer questions on today's skill on my own, without help.
  • I can explain each step and say why it works.
  • I can check my answer and spot a mistake.

Before and after

Needs first: Plant and animal cells

Leads to: Measure tiny things in mm, µm and nm

Materials: Microscope images or slides, Cell diagrams, Mini whiteboards, A diagram or short video clip of the idea, Printed student sheet (below).

Warm-up · 4 min

  • Quick retrieval from earlier learning (Plant and animal cells). Students answer on mini whiteboards.
  • Show answers together and note who needs support in the main task.
  1. Which part of a cell contains the genetic material? (cell wall / mitochondria / cell membrane / nucleus) → nucleusPrompt: Think about which parts are only in plant cells.
  2. Cells: which statement is NOT true? (All plant cells have chloroplasts. / Chloroplasts are found in plant cells, not animal cells. / Most plant cells have a large permanent vacuole. / Both plant and animal cells have a nucleus, cytoplasm and a cell membrane.) → All plant cells have chloroplasts.Prompt: Do plant cells respire?
  3. Which part of a cell absorbs light for photosynthesis? (nucleus / chloroplasts / cell membrane / cell wall) → chloroplastsPrompt: Think about which parts are only in plant cells.

Hook · 3 min

  • Show a microscope image of cells and ask what students think they are looking at.
  • Share the objective: Microscopes and magnification. Read the success criteria together.

I do: model it · 7 min

  • Work through the example out loud, saying why you do each step, not just what you do.
  • Example: A microscope has a ×10 eyepiece lens and a ×10 objective lens. What is the total magnification?
  • Step 1: 10 × 10 = 100
  • Step 2: So the answer is: ×100
  • Answer: 100
  • Pause after each step and ask a student to say what comes next.

We do: guided practice · 6 min

  • Do these together. Students try each step on whiteboards before you reveal it.
  • Use the hints as prompts rather than giving the answer.
  1. A microscope has a ×15 eyepiece lens and a ×10 objective lens. What is the total magnification? → 150Prompt: Combine the two lenses.
  2. A cell is 0.1 mm wide. It is viewed at ×200. How wide is the image, in mm? → 20 mmPrompt: magnification = image size ÷ actual size

You do: independent practice · 7 min

  • Students work on the student sheet. Circulate and check the first two answers of every student early.
  • Students who finish: write a question of their own for a partner, with the answer.

The 6 questions are on the student sheet below, with answers in the key.

Exit ticket · 3 min

  • Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
  1. An image of a cell is 1.6 mm wide at ×200. What is the real width of the cell, in micrometres (µm)? (1 mm = 1000 µm) → 8 µmPrompt: actual size = image size ÷ magnification
  2. A cell is 0.05 mm wide. It is viewed at ×200. How wide is the image, in mm? → 10 mmPrompt: magnification = image size ÷ actual size

Watch out for

  • Everyday meanings of words getting in the way of the science meaning: define key words explicitly.
  • Remembering facts without the reason: ask "why?" and "what is the evidence?"

Support and stretch

Support

  • Review first: Plant and animal cells.
  • Use concrete materials: microscope images or slides.
  • Give the first step of each question, or a partly worked example to finish.
  • Pair with a confident partner for the guided practice.

Stretch

  • Move on to: Measure tiny things in mm, µm and nm.
  • Explain a common mistake in writing and how to fix it.
  • Write a word problem that uses today's skill, then solve a partner's.

Homework and more practice

Free online practice with hints and printable worksheets for this skill: eurekami.com/science/grade-7.

Free lesson plan from eurekami.com/lesson-plan-builder

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Microscopes and magnification

Name

Date

Score/ 6

  1. Question 1

    A cell is 0.05 mm wide. It is viewed at ×200. How wide is the image, in mm?

    Answermm

  2. Question 2

    An image of a cell is 12.5 mm wide at ×500. What is the real width of the cell, in micrometres (µm)? (1 mm = 1000 µm)

    Answerµm

  3. Question 3

    A microscope has a ×10 eyepiece lens and a ×100 objective lens. What is the total magnification?

    Answer

  4. Question 4

    A cell is 0.01 mm wide. It is viewed at ×400. How wide is the image, in mm?

    Answermm

  5. Question 5

    A microscope has a ×5 eyepiece lens and a ×4 objective lens. What is the total magnification?

    Answer

  6. Question 6

    An image of a cell is 4 mm wide at ×200. What is the real width of the cell, in micrometres (µm)? (1 mm = 1000 µm)

    Answerµm

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Answer key: Microscopes and magnification

  1. 1. 10 mm

  2. 2. 25 µm

  3. 3. 1000

  4. 4. 4 mm

  5. 5. 20

  6. 6. 20 µm